Polyacetal compositions generally are understood to include homopolymers of formaldehyde as well as copolymers of formaldehyde with other monomers that yield oxyalkylene groups having two or more carbon atoms in the main polymer chain. Polyacetals possess a desirable balance of physical properties including high stiffness, toughness, low coefficient of friction and good solvent resistance. Polyacetals are commercially available in a range of viscosities which are suitable for forming finished articles by compression molding, injection molding and extrusion. However, even the most viscous commercially available polyacetals are not suitable for the preparation of larger finished articles (i.e., larger than a few 100 cc) by extrusion blow molding.
This is unfortunate because many hollow articles such as containers and complex automobile parts; e.g., air ducts, are difficult and expensive to manufacture by compression or injection molding. Of course, such hollow articles are readily and economically made by blow molding from polymers having melt rheologies that are suited to blow molding.
Thus a need exists for polyacetal compositions which are readily processible by blow molding techniques and which at the same time substantially retain the outstanding properties associated with polyacetals.